Black-out lamp



June 1942- K. P. swANsoN 2, 5

BLACKOUT LAMP I Filed Feb. 9, 1942 Invenioi:

Patented June 16, 1942 2,286,657 BLACK-OUT LAMP Kenneth P. Swanson, North Valley Stream, Long Island, N. Y., assign to Wabash Appliance Uorporation. Brooklyn, N. Y., a corporation of New York Application February 9, 1942, Serial lilo. 430,007 3 Claims. (Cl. 176-34) that may be set off .for special treatment in the bulb in accordance with the color or intensity of the light which it is desired to transmit. For example, the bulb may be shaped toinclude a pro-' jecting cylindrical portion of reduced diameter terminating in a curved circular end wall and this cylindrical portion or its end wall is thus conveniently located and disposed for treatment by dipping, spraying or otherwise to determine and establish its light-transmitting properties.

As herein shown and as another desirable feature, there is preferably employed in the lamp of my invention a bulb provided with an inner or inwardly directed metallic reflecting coating which not only prevents the escape of light rays through the body of the bulb, but concentrates and directs the light of the filament to the colored or partially obscured transmitting area. While the reflecting coating may in some instances be by itself efiective as a complete light screen I prefer to supplement it by an exterior coating or film of an opaque heat-resisting character. This may be disposed co-extensive with respect to the inner reflecting surface and may extend from the base of the lamp to the boundary of the treated light-transmitting portion of the bulb. The lamp of my invention is thus efficient, has proved durable in use and may be placed in light sockets already available on commercial service circuits.

These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing in which,-

Fig. 1 is a view of the .lamp in elevation,

Fig; 2 is a view in partial longitudinal section,

and

Fig. 3 is a fragmentary view, partially in cross section, showing the various coatings on the bulb in exaggerated thickness;

The bulb herein shown has a main glass body portion III with side walls which are approximately cylindrical but diverge outwardly from the base to a slight degree and then merge through an inwardly curved annular shoulder into a short cylindrical portion ll of reduced diameter as compared to the rest of the bulb. The cylindrical portion ll of the bulb terminates in a curved end wall l2 of flattened convexity. The bulb has the usual threaded metallic base l3 and center terminal M which together pro- 1 vide terminals for the filament circuit. The bulb is provided with a mount and filament l5 of any usual or conventional character. 1

The inner wall of the bulb is provided with a metallic coating l6 of aluminum or silver which extends continuously from the base up to a circumferential line defining the end wall area of the bulb. The reflecting coating may be applied to the inner bulb surface by any of the several available commercial processes; for example, by that disclosed in U. S. Letters'Patent No. 2,l93,-- 555, granted March 12, 1940, to Birdseye Electric Corporation. In accordance with that patent the inverted lamp bulbmay be partially filledwith a silver depositing solution that is caused to fiow continuously over the glass surface until a continuous silver coating has been deposited on the glass. This has a high light reflecting efllciency and is also substantially impervious to the passage of light rays. The convex end wall I! of the projecting cylindrical portion ll of the'bulb is then provided with a coating of translucent, heat resistant solution, for example, sodium silicate'carrying a blue or red or other colored pigment. The lamp is completed by providing the exterior surface of r the body It with a similar coating of black color which extends from the base -up to the circumferential line of colored coating upon the convex end wall of the bulb. This exterior coating sup.-'

plementsv the internal reflecting coating of the bulb body, thus rendering it completely impervious to the passage of light rays. The boundary of the colored coating is herein shown as located somewhat below the edge of the circular end wall l2 of the cylindrical portion ll so that a short portion of the cylindrical wall is included in the light-transmitting area of the lamp, but

the exact location of this boundary lineis not important so long as the entire end wall is included. However, for convenience in spraying it is desirable that the boundary line of the translucent area should lie in a cylindrical portion of the bulb. It will be noted that practically the entire bulb surface except its light transmitting area is provided with two light-confining coatings, the inner reflecting coating and the outer black coating. This. feature contributes to the production ing should be of a reflecting character'as the lighting efliciency of the lamp is thereby improved.

It is preferred to employ a solution of sodium silicate with a black or colored pigment for the coating material since this is heat-resistant and r is not impaired by the heat of the lamp even in long periods of continuous use. may be sprayed directly upon the warmed bulb of the lamp and quickly dried and baked thus providing a. permanent, vapor-free: coating. Two or more coatings may be applied to the bulb if desired, although as a general thing the employment of a metallic coating with a single Moreover, it

claim as new Patent:

1. An electric incandescent blackout lamp comprising a bulb having a main body portion and a projecting portion of reduced diameter terminating in a circular convex end wall, a filament in the bulb, a substantially-opaque metallic reflecting coating on the body of the bulb for directing rays from the filament into the projecting portion of the bulb, and a colored translucent heat-resistant coating covering-at least the circular end wall of said reduced portion,

2. An electric incandescent blackout lamp comprising a bulb having a filament-containing body portion defined by approximately cylindrical but slightly divergent side walls, the latter merging through a convex annular shoulder into a short cylindrical portion of reduced diameter terminating in a circular convex end wall, the body portion being provided internally with a substantially opaque metallic reflecting coating and externally with a substantially opaque coating of a I black pigment in sodium silicate, the said coatexternal silicate coating results in a bulb which is opaque in its areas of superposed coatings.

When a bulb provided with an internal reflecting surface is used the entire luminous energy of the lamp is directed through the colored or partially obscured light-transmitting end wall and the latter is caused to glow vigorously with an intense blue or red light which 'while useful within a short range, is not visible at any substantial distance.

The lamp of my invention has been found entirely satisfactory in use, being durable, eflicient,

pleasing i'n'appearance, and providing a limited source of blue or red light rays of an intensity which may be readily controlled by varying the thickness of the colored coating upon the circular convexend wall of the lamp.

Having thus disclosed my invention and described one illustrative embodiment thereof, I

ings terminating substantially together in a boundary line extending about the short cylindrical portion of the bulb, and the remainder oi. said short cylindrical portion, including its end wall, having an external, heat-resisting pigmented translucent coating.

3. An electric incandescent blackout lamp comprising a bulb having a base and a filament-containing body portion defined by approximately cylindrical but slightly flaring side wal1s, the latter merging into a short cylindrical portion of reduced diameter terminating in a circular convex end wall, said short cylindricalportion having on at least its said end wall an external heatresisting pigmented translucent coating, and said body portion having an internal metallic reflecting coating and'an external opaque heat-resisting coating which extend from the base coextensively to the boundary line of .said pigmented coating in the said short cylindrical portion of the bulb.

KENNETH P. SWANSON.

and desire to secure by Letters 

